The early diagnosis of pathogenic infections may help reduce the number of incidents of disease and fatalities caused by pathogenic infections in humans. Infections may be further reduced by the detection of pathogenic agents in water or food before consumption. Traditional pathogen detection methods such as polymerase chain reaction, immunology-based methods and culture and colony counting generally take a long time to provide accurate results and can be expensive and inaccessible in remote locations. To address this problem, a variety of biosensors that detect biomolecules for diagnostic or quality control purposes have been developed.
Electrochemical biosensors are sensors used to detect target biomolecules suspended in a solution by means of molecular recognition. A typical electrochemical biosensor includes at least one electrode with biological recognition components immobilized on the surface of the electrode which are able to bind to or complex with target biomolecules in the solution. The biological recognition components may be pathogens or antigens, antibodies, enzymes or nucleic acids for example. The biosensors are configured to measure changes in the conductivity of the electrode due to the binding or complexation of biomolecules from a solution to the biological recognition components immobilized on the electrode. In effect, changes in the resistance of the electrode when connected in an electric circuit to which a constant potential difference and current is applied, is measured.
Recent developments in the field of electrochemical biosensing have resulted in the use of so-called “electrotextiles”, which are membranes that consist of polymer fibers that have been coated with a conductive polymer coating, as the electrode. The microfibers provide a large surface area for the immobilization of a substantial amount of the biological recognition components on the surface of the electrode.
The applicant is aware of a laboratory-scale system in which an electrotextile is submerged in a buffer solution and connected to a circuit by means conductive metal clips that serve as electrodes. Both the electrotextile and clips are submerged in a solution containing sodium chloride, potassium chloride, sodium phosphate and potassium phosphate salts. The sample solution containing biomolecules to be detected is then added to the buffer solution and changes in the conductivity of the electrotextile after addition of the sample solution is measured. However, the submerged electrodes participate in electrochemical reactions with the salts in the solution, producing a substantial background effects during the detection process which reduces the sensitivity of the system. As a result of being submerged in a saline solution, the electrodes are also susceptible to degradation over time caused by redox reactions on the surface of the electrodes. The system also needs a relatively large volume of buffer solution, which may not be readily available outside of a laboratory environment.
In general, existing systems that utilize electrotextiles for the detection of biomolecules are complex, laboratory-scale systems that may not be suitable for use in the field or re-use and may not be sensitive enough to be used with very small fluid samples. There thus remains a need for a cost-effective, versatile, sensitive and robust device for detecting the presence of biomolecules. Ideally the device must be of a relatively simple construct and easy to use so that it may be utilized in the field in order to rapidly detect biomolecules linked to pathogenic infection or contamination.
The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.